Just over 1.4 million people went through Transportation Security Administration airport checks Wednesday. Daily volume had been closer to 2 million for much of the summer, but it’s been dropping off lately. And airlines appear to be worried. 

United, American, JetBlue, Delta, and Southwest all said Thursday that they’re tempering their expectations for the fall after bookings went down in August and cancellations rose. 

The end of summer pretty much always coincides with some drop in air travel. Even in non-pandemic times.

“The period between Labor Day and Thanksgiving is known in the airline industry as a shoulder season,” said Henry Harteveldt, a travel industry analyst at Atmosphere Research Group. What’s different, he said, “is that right now, of course, is the time when businesspeople would normally be traveling, and we have far fewer people traveling for business today.”

And fewer people taking trips for fun.

Richard Aboulafia, an aviation analyst at Teal Group, said that trend began to show up in August when more people started canceling trips and fewer people were booking new ones. 

“The summer was looking great, but because of the resurgence of the pandemic in the form of the delta variant, that’s having a very negative impact on travel. The recovery just isn’t as robust as we had hoped for,” Aboulafia said.

Air travel rebounded faster in the U.S. than in other parts of the world this summer, as vaccines rolled out and the country largely reopened.  

But now, Aboulafia said, it’s Europe that’s seeing more of a bump.

“They’ve simply been able to accept vaccine passports, a higher level of vaccination, and … a higher level of testing,” he said.

In the U.S., with fewer people booking trips, some airlines are cutting back capacity again. 

Adit Damodaran, an economist at the travel site Hopper, said they’re also cutting ticket prices. 

“Airfare is dropping going into the fall for both domestic and international flights,” Damodaran said.

That, he added, is tempting for a lot of travelers. 

But right now, most people who are booking aren’t doing it very far in advance.